Fix Drupal ~10.3.0 compatibility of styling of back-end sidebar when editing content

Problem/Motivation

Facing the mismatched sidebar styling for the back-end editing page after updating to Drupal ~10.3.0

Name of classes and template was changed in form-two-columns.html.twig and the node-edit-form.html.twig template files
Old .layout-region--node-main class was deprecated and the new classes like .layout-region--main will work in all edit forms of entity types

Proposed resolution

• #3456503: Update Drupal Core to ~10.3.0 and ~11.0.0 and drop support for ~9.5.0 in Vartheme Claro version requirements
• Update libraries overrides to latest changes with Claro ~10.3.0
• Change the custom styling in Vartheme Claro to follow up with latest Drupal Core ~10.3.0 changes

Remaining tasks

• ✅ File an issue about this project
• ✅ Addition/Change/Update/Fix to this project
• ✅ Testing to ensure no regression
• ➖ Automated unit/functional testing coverage
• ➖ Developer Documentation support on feature change/addition
• ➖ User Guide Documentation support on feature change/addition
• ➖ UX/UI designer responsibilities
• ➖ Accessibility and Readability
• ✅ Code review from 1 Varbase core team member
• ✅ Full testing and approval
• ✅ Credit contributors
• ✅ Review with the product owner
• ✅ Update Release Notes and Update Helper on new feature change/addition
• ✅ Release varbase-9.1.4, vartheme_claro-3.0.16

Varbase update type

• ✅ No Update
• ➖ Optional Update
• ➖ Forced Update
• ➖ Forced Update if Unchanged

User interface changes

API changes

• N/A

Data model changes

• N/A

Release notes snippet

• Issue #3456508: Fixed Drupal ~10.3.0 compatibility of styling of back-end sidebar when editing content